xdp: base API for new XDP rx-queue info concept
This patch only introduce the core data structures and API functions. All XDP enabled drivers must use the API before this info can used. There is a need for XDP to know more about the RX-queue a given XDP frames have arrived on. For both the XDP bpf-prog and kernel side. Instead of extending xdp_buff each time new info is needed, the patch creates a separate read-mostly struct xdp_rxq_info, that contains this info. We stress this data/cache-line is for read-only info. This is NOT for dynamic per packet info, use the data_meta for such use-cases. The performance advantage is this info can be setup at RX-ring init time, instead of updating N-members in xdp_buff. A possible (driver level) micro optimization is that xdp_buff->rxq assignment could be done once per XDP/NAPI loop. The extra pointer deref only happens for program needing access to this info (thus, no slowdown to existing use-cases). Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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@ -20,6 +20,7 @@
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#include <linux/set_memory.h>
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#include <linux/kallsyms.h>
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#include <net/xdp.h>
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#include <net/sch_generic.h>
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#include <uapi/linux/filter.h>
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@ -503,6 +504,7 @@ struct xdp_buff {
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void *data_end;
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void *data_meta;
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void *data_hard_start;
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struct xdp_rxq_info *rxq;
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};
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/* Compute the linear packet data range [data, data_end) which
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47
include/net/xdp.h
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include/net/xdp.h
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/* include/net/xdp.h
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*
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* Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
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* Released under terms in GPL version 2. See COPYING.
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*/
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#ifndef __LINUX_NET_XDP_H__
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#define __LINUX_NET_XDP_H__
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/**
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* DOC: XDP RX-queue information
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*
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* The XDP RX-queue info (xdp_rxq_info) is associated with the driver
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* level RX-ring queues. It is information that is specific to how
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* the driver have configured a given RX-ring queue.
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*
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* Each xdp_buff frame received in the driver carry a (pointer)
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* reference to this xdp_rxq_info structure. This provides the XDP
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* data-path read-access to RX-info for both kernel and bpf-side
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* (limited subset).
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*
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* For now, direct access is only safe while running in NAPI/softirq
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* context. Contents is read-mostly and must not be updated during
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* driver NAPI/softirq poll.
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*
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* The driver usage API is a register and unregister API.
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*
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* The struct is not directly tied to the XDP prog. A new XDP prog
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* can be attached as long as it doesn't change the underlying
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* RX-ring. If the RX-ring does change significantly, the NIC driver
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* naturally need to stop the RX-ring before purging and reallocating
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* memory. In that process the driver MUST call unregistor (which
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* also apply for driver shutdown and unload). The register API is
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* also mandatory during RX-ring setup.
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*/
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struct xdp_rxq_info {
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struct net_device *dev;
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u32 queue_index;
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u32 reg_state;
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} ____cacheline_aligned; /* perf critical, avoid false-sharing */
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int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
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struct net_device *dev, u32 queue_index);
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void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq);
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void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq);
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#endif /* __LINUX_NET_XDP_H__ */
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@ -11,7 +11,7 @@ obj-$(CONFIG_SYSCTL) += sysctl_net_core.o
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obj-y += dev.o ethtool.o dev_addr_lists.o dst.o netevent.o \
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neighbour.o rtnetlink.o utils.o link_watch.o filter.o \
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sock_diag.o dev_ioctl.o tso.o sock_reuseport.o \
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fib_notifier.o
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fib_notifier.o xdp.o
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obj-y += net-sysfs.o
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obj-$(CONFIG_PROC_FS) += net-procfs.o
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67
net/core/xdp.c
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net/core/xdp.c
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/* net/core/xdp.c
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*
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* Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
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* Released under terms in GPL version 2. See COPYING.
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*/
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <net/xdp.h>
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#define REG_STATE_NEW 0x0
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#define REG_STATE_REGISTERED 0x1
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#define REG_STATE_UNREGISTERED 0x2
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#define REG_STATE_UNUSED 0x3
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void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq)
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{
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/* Simplify driver cleanup code paths, allow unreg "unused" */
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if (xdp_rxq->reg_state == REG_STATE_UNUSED)
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return;
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WARN(!(xdp_rxq->reg_state == REG_STATE_REGISTERED), "Driver BUG");
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xdp_rxq->reg_state = REG_STATE_UNREGISTERED;
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xdp_rxq->dev = NULL;
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}
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EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg);
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static void xdp_rxq_info_init(struct xdp_rxq_info *xdp_rxq)
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{
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memset(xdp_rxq, 0, sizeof(*xdp_rxq));
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}
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/* Returns 0 on success, negative on failure */
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int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
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struct net_device *dev, u32 queue_index)
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{
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if (xdp_rxq->reg_state == REG_STATE_UNUSED) {
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WARN(1, "Driver promised not to register this");
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return -EINVAL;
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}
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if (xdp_rxq->reg_state == REG_STATE_REGISTERED) {
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WARN(1, "Missing unregister, handled but fix driver");
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xdp_rxq_info_unreg(xdp_rxq);
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}
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if (!dev) {
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WARN(1, "Missing net_device from driver");
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return -ENODEV;
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}
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/* State either UNREGISTERED or NEW */
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xdp_rxq_info_init(xdp_rxq);
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xdp_rxq->dev = dev;
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xdp_rxq->queue_index = queue_index;
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xdp_rxq->reg_state = REG_STATE_REGISTERED;
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return 0;
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}
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EXPORT_SYMBOL_GPL(xdp_rxq_info_reg);
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void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq)
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{
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xdp_rxq->reg_state = REG_STATE_UNUSED;
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}
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EXPORT_SYMBOL_GPL(xdp_rxq_info_unused);
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